Pump loss-of prime automatic shut off valve

ABSTRACT

A pump shutoff device is provided wherein compressed air supplied to the air inlet port of the over speed control device enters an air pressure chamber, and then proceeds to an adjacent air exhaust chamber. From there, the air passes to an outport which is connected,directly to the inlet port of the air motor of an air-operated piston pump spool located inside the body of the device, is shaped such that the valve spool functions to allow passage of air freely from the air pressure chamber to the air exhaust chamber. Compressed air is connected through a series of unrestricted conduits,ports and chambers continuous from the compressed air supply to the air motor of a pump. The air motor is energized by compressed air to provide continuous pumping. 
     Positive pressure existing in the fluid pressure chamber exerts an axial thrust on the spool. Adjacent to the air chambers and opposite the position of the fluid pressure chamber is a coil compression spring. The spool and the spring are shaped so as the spring is compressed it exerts an axial force on the spool in opposition to the axial force on the spool exerted by the fluid pressure chamber

FIELD OF THE INVENTION

The present invention relates to a loss-of-prime automatic shunt offvalve for use with air operated pumps of the kind used primarily for oiland grease dispensing equipment in facilities that service motorvehicles, such as quick lube service centers, automobile dealershipservice departments, truck fleet garages and the like.

BACKGROUND OF THE INVENTION

When pumps such as compressed-air-driven piston pumps are inoperation,they generate a (pumped) fluid pressure at the pump outputport. This pressure effect is due to the fact that the pump is pushingfluid from the pump. This pressure is maintained so long as; 1) thepump, is energized with compressed air; 2) the pump is attached to theoutput load;and 3) the pump is primed so as to continuously induct fluidfrom the supply reservoir.

If an air leak occurs in the incoming suction line from the reservoir tothe pump, or if the pump reservoir level is allowed to deplete and rundry during pump operation, then a loss of prime occurs within the pump.Upon loss of prime, the air-driven pump,attached to an open andpressurized air entry connection, continues to cycle and it therebypumps air instead of fluid. Because air (instead of fluid) is movingagainst an attached load in pumps of this kind,a much lower pressure isproduced at the pump outport port and the pump responds by acceleratingand then cycles at a very rapid and often damaging cyclefrequency.Additionally, during loss of prime,piston seals in the fluidpumping chamber of the pump are purged clean of the pumped fluid and aredamaged because the fluid also typically serves to lubricate thoseseals. Specifically,friction heat is generated and the seals which areno longer submerged,and the pump itself, are subjected to damageparticularly when allowed to run for a sustained period in an unprimeddry condition. Rapid pump cycling plus dry seal contact leads tounacceptable levels of seal heating and therefore to rapid seal failurefrom wear or deformation.

It is accordingly desirable to provide a means to protect pumps of thiskind,so that they do not continue to cycle whenever a lodd of primeexists, thereby preventing seal damage during such conditions. It isalso desirable to create an indication of the unprimed pumpcondition,alerting the user so that prompt action can be taken torestore prime and remedy the problem.

While prior attempts have been made to alleviate the damage resultingfrom original damage that occurs to pumps and seals whenfluid in thereservoir is depleted or functionally inadequate,at the present time noknown practical and adequate solution has been identified. Forexample,the device available as ARO STOP® Pump Saver Control Valve ofthe Ingersoll-Rand Company, described in that company's one page productservice brochure designated 23644-400, has been found to lack variousrequirements. For example,devices of this kind fail to shut off pumpoperation is and when the pump suddenly draws in compressed air at amore rapid rate. In practice, when a typical pump loses prime,theincreased cycle frequency and therefore the increased rate of flow ofcompressed air into the pump often is insufficient in magnitude totrigger this kind of shut off means.

The reference to “fluid” herein is taken to mean both self-levelingliquids such as oil and non-self-leveling but pumpable materials such asgreases.

SUMMARY OF THE INVENTION

The present invention provides a novel automatic speed control devicefor air operated pumps that functions to automatically stop operation ofthe air-operated pumps whenever loss of prime occurs. The control deviceutilizes the fluid output pressure of the pump as a feedback element toprovide the necessary control.

BRIEF DESCRIPTION OF THE FIGURES

FIG. 1 illustrates schematically the location of the speed controldevice of the invention in a typical pump and reservoir system.

FIG. 2 is a side view of the speed control device of the invention shownin a continuous pumping mode.

FIG. 3 is a view similar to that of FIG. 2 with the speed control deviceof the invention shown in the interrupt pump-off mode.

FIG. 4 is a perspective view of the speed control device of theinvention in the interrupt or pump-off mode and with the body of thecontrol device section cut away to reveal the device interior.

DETAILED DESCRIPTION OF THE INVENTION

While the invention is described primarily with the application of anautomatic shut off valve for use with a reciprocating piston air pump,it will be apparent to those skilled in the art that the invention isapplicable for use also in conjunction with rotary air operated pumps.

Reference to FIG. 1 of the drawing shows the placement of the over speedcontrol device of the invention when installed for use in conjunctionwith a pumping system. The speed control device of the invention 109 ismounted between the incoming compressed air supply line 106 (air line106 being a pressure hose,tube or other suitable conduit for compressedair) and the supply air line 104 to the pump air motor 101 aconventional limit that comprises an air-operated fluid piston pump 102and motor 101. The fluid pump 102 is connected to a pump outlet path 105which comprises a fluid line or lines having a branch 112 connected tothe fluid input port 11 (see also FIG. 2) of the over speed device 109and another branch 110 attached to a fluid flow network,functioningthereby through a fluid resistance load 107, and then outward for usefuldispensing of the pumped fluid. The fluid resistance load consists ofpiping, hose reels, dispense control handles and other conventionalcomponents which conduct and control the movement of fluid to one moredisensing points.

Reference to FIG. 3 shows details of the over speed control device ofthe invention while in the continuous pumping mode. As illustrated inFIG. 3, compressed air is supplied to the air inlet port 8 of the overspeed conrtol device; the air immediately enters an air pressure chamber9,and then proceeds to an adjacent air exhaust outlet chamber 10. Fromthere, the air passes to an output port 7 which is connected, directlyor by a hose or enclosed passage, to the inlet port of the air motor 101(see FIG. 1) of an air-operated piston pump (101 and 102). A valve spool13 located inside the body 1 of the device, is shaped so that, in thevalve spool position shown in FIG.3,air passes freely from the airpressure chamber 9 to the air exhaust chamber 10. Thw free passage ofthe compressed air connected through a series of conduits, ports andchambers is continuous from the compressed air supply to the air motorof the pump and is unrestricted in the condition of the speed controldevice shown in FIG. 3. In such condition,the air motor is beingenergized by compressed air to provide continuous pumping.

Referring again to FIG. 3, a fluid pressure chamber 2 contiguous to thefluid input port II is provided,exposed to one end of the spool 13 suchthat any positive pressure which might exist in the fluid pressurechamber 2 exerts an axial thrust on the spool 13. Also,adjacent to andaligned with the air chambers 9, 10, and opposite the position of thefluid pressure chamber 2,a spring body chamber 3 is provided,containinga coil compression spring 12. The spool 13 and the spring body chamber 3are shaped so as to create shoulders which contact, contain and contractthe ends of the spring 12 and substantially compress it during thecondition shown in FIG. 3. The spring 12 thereby exerts an axial forceon the spool 13 in opposition to the axial force on the spool 13 exertedby the fluid pressure which occurs via chamber 2.

Reference is now made to FIG. 2 which shows details of the over speedcontrol device of the invention while in the interrupted, or pump off,mode. As shown in FIG. 2, the valve spool 13 is shifted to a springcompressing position. The shape of the spool is such that, in theposition shown in FIG. 2 compressed air is interrupted and cannot passfrom air pressure chamber 9 to the adjacent air exhaust chamber 10 dueto the sealed closure of the passage. Accordingly, in the spool positionof FIG. 2, air provided for operation of the air motor 101 isinterrupted and the pump cannot be energized and therefore becomesinoperable.

In the operable and inoperable stages of the over speed control valveshown in FIGS. 3 and 2 respectivly,the size and force of the spring, aswell as the size and force of the spool-end area exposed to pressure inthe fluid body chamber, are selected to obtain the following conditions:

Condition 1: If pressure in the fluid pressure chamber 2 is greater thanany pressure which would occur there when the pump displaces air only(unprimed),then the axial force on the spool (13) due to fluid pressureexceeds the axial forces on the spool 12 due to the spring (12) and alsodue to internal friction of parts. In this condition (pump operable),thespool will shift to the arrangement of FIG. 3 and will be maintained inthat position.

Condition 2: If pressure in the fluid pressure chamber 2 is less than orequal to any pressure which would occur there when the pump displacesair only (unprimed), then the axial force in the spool 13 due to fluidpressure is less than the axial forces on the spool 13 due to the spring12 and also due to internal friction of parts. In this condition,thespool will shift to the arrangement of FIG. 2 (pump inoperable) and willbe maintained in that position.

Due to the capability of the speed control device 109 to provideconditions 1 and 2, the pump will be energized and will operatecontinuously whenever it is in a primed condition as in condition 1. Itwill cease operation promptly whenever a primed pump condition is lostas in condition 2. The device therefore functions to stop all operationof the pump in the presence of an unprimed condition,thereby preventingpump and seal damage.

When the pump does not operate on command when a dispense valve isopened, the service operator will be alerted to the pump's unprimedcondition, so this will prompt a remedying of the condition, avoidingpump damage that would otherwise occur.

In order to provide a means of initially operating the pump to obtain afirst condition of prime a suitable mechanism such as a pull handle 6 isprovided, (shown in FIGS. 2 and 3), to manually displace the spool to anair-open condition and cycle the pump until the line is filled withfluid and pressurized. Thereafter, the pump will maintain this operablecondition due to its primed condition and sufficient pressure existingin the fluid body chamber 2.

While the invention has been described with reference to the preferredembodiments, it will become apparent to those skilled in the art thatmany modifications and variations to details can be derived from thedescription provided. Accordingly the invention is intended to includeall such variations and modifications encompassed within the appendedclaims.

1. An over speed control device for fluid pumps comprising: a) Alongitudinal assembly; b) An air inlet chamber contained in saidassembly; c) An air inlet port to said chamber; d) An air pressurechamber aligned and on the opposite side of said air inlet chamber; e)An air exhaust chamber aligned and on the opposite and aligned with saidinlet air chamber; f) An air outlet port from said air exhaust chamberprovided for connecting to an inlet part of a pump air motor; g) A valvespool in said assembly positioned contigenous to said air exhaustchamber; and h) A compression coil spring arranged to exert axialpressure on said valve spool; said air inlet chamber,air exhaustchamber,valve spool and compressor spring being arranged such that whenpositive pressure is exerted in the air pressure chamber a force is thenapplied on the valve dpool,compressing said coil spring whereby saidspool is shifted and thereby interrupts and prevents passage ofcomressed air from said air inlet chamber to said air exhaust chamber.2. The over speed control device of claim 1 provided with associatedmechanism to obtain an initial condition of pump prime.
 3. The device ofclaim 2 wherein the associated mechanism compromise a handle that whenpulled manually functions to dispense the valve spool to an air opencondition.
 4. The speed control device of claim 1 in functionalcombination with a responding piston air pump.
 5. The speed controldevice of claim 1 in functional combination with a rotary air operatedpump.
 6. The overspeed control device of claim 1 wherein acontinually-compressed gas in the spring body chamber is used in placeof a mechanical spring.
 7. A method for automatically shutting down aitoperated fluid dispensing pumps upon loss of pump prime comprisingspring-means to permit an open passage for the dispensing of fluid fromthe pump so long as fluid prime exists, said spring-means being extendedto stop the pumped air supply and shut off the fluid passage upon lossof prime due to air leakage or fluid supply depletion and fluid pressuremeans fuctioning to compress sain spring-means and enable air supply anddispensing of fluid when fluid prime is restored.